VOLTAGE-DEPENDENT CHLORIDE CHANNELS - INVERTEBRATES TO MAN

Chloride channels are ubiquitous proteins found in invetebrates to man . Cl- is one of the most abundant biological anions and accounts for a measurable fraction of the electrical conductance of many biological membranes. Physiologically this contributes to cellular processes, inc luding pH regulation, volume regulation, generation of the resting mem brane potential, and regulation of membrane excitability. The unitary conductance of voltage-dependent Cl- channels is as diverse as the num ber of different types of Cl- channels described ranging from 5-450 pS . Cl- channels are highly anion selective passing at least ten anionic species, including all of the halides. Cl- channels are blocked by va rious agents, including aromatic acids, inorganic cations, and protons . Maintaining high resting conductance and normal excitability, regula ting cell volume, and modulating hormone action are some examples of t he functions of Cl- channels. Despite the large amount of data accumul ated on voltage-dependent Cl- channels, identifying subsets within thi s class of channels with coherent biophysical features that subserve e ach specific function is still not possible. At present, the molecular structure for every type of functional Cl- channels has not been dete rmined, but future identification of cloned Cl- channel structures sho uld provide a clearer understanding of the functional properties of ba ckground Cl- channels. (C) 1996 Wiley Liss, Inc.